Process for the preparation of carbodiimide-isocyanurate foams

ABSTRACT

Rigid cellular foam compositions characterized by carbodiimide and isocyanurate linkages are prepared by catalytically condensing an organic polyisocyanate in the presence of a sufficient amount of a co-catalyst system of methanol and a tertiary amine trimerization catalyst.

United States Patent 1 Narayan et a].

PROCESS FOR THE PREPARATION OF CARBODIIMlDE-ISOCYANURATE FOAMSInventors: Thirumurti L. Narayan, Riverview;

Moses Cenker, Trenton, both of Mich.

BASF Wyandotte Corporation, Wyandotte, Mich.

Filed: Dec. 21, 1973 Appl. No.: 427,122

Assignee:

References Cited UNITED STATES PATENTS 2/1965 Beitchman 260/25 AW11/1971 Diehr 260/2.5 BF 2/1972 Kan 260/25 AW June 3, 1975 3,657,1614/1972 Bernard 260/25 AW 3,723,364 3/1973 McLaughlin 260/25 AC 3,723,3663/1973 Kan 260/25 BF FOREIGN PATENTS OR APPLICATIONS 908,337 10/1962United Kingdom 260/25 AW 842,420 7/1960 United Kingdom PrimaryExaminerDonald E. Czaja Assistant ExaminerC. Warren Ivy Attorney, Agent,or Firm-Joseph D. Michaels; Bernhard R. Swick; Robert E. Dunn [5 7]ABSTRACT Rigid cellular foam compositions characterized by carbodiimideand isocyanurate linkages are prepared by catalytically condensing anorganic polyisocyanate in the presence of a sufficient amount of aco-catalyst system of methanol and a tertiary amine trimerizationcatalyst.

8 Claims, N0 Drawings PROCESS FOR THE PREPARATION OFCARBODIIMIDE-ISOCYANURATE FOAMS BACKGROUND OF THE INVENTION 1. Field ofthe Invention The present invention relates to a novel catalyst systemfor the preparation of cellular foams characterized by carbodiimide andisocyanurate linkages. More particularly, the invention relates to theuse of a cocatalyst system of methanol and a tertiary amine in thepreparation of cellular foams characterized by carbodiimide andisocyanurate linkages.

2. Prior Art The preparation of foams containing carbodiimide linkagesis well known in the art. Generally, the foams are prepared bycondensing an organic polyisocyanate with a catalyst which promotescarbodiimide linkages, optionally in the presence of a blowing agent.Representative of such teachings are the disclosures found in US. Pat.No. 2,941,966 and 3,645,923. The prior art also teaches that foamscontaining both carbodiimide and isocyanurate Nos. can be prepared bycondensing an organic polyisocyanate with a catalyst which promotes bothcarbodiimide and isocyanurate linkages or with a co-catalyst system, onecatalyst promoting carbodiimide linkages and one catalyst promotingisocyanurate linkages. Representative of such teachings are thedisclosures found in US. Pat. Nos. 3,645,923; 3,657,161; 3,717,596;3,723,366, and 3,746,709.

SUMMARY OF THE INVENTION The present invention relates to an improvedprocess for the preparation of carbodiimide-isocyanurate foams employinga catalytically sufficient amount of methanol and a tertiary aminetrimerization catalyst. It was surprising and unexpected to find thatthe use of a co-catalyst system of methanol and a tertiary amineprovides for foams characterized by carbodiimide linkages sinceheretofore catalysts such as s-triazines and phospholene oxides wereemployed for this purpose.

DESCRIPTION OF THE PREFERRED EMBODIMENTS In accordance with the presentinvention, rigid cellular foams are prepared by the catalyticcondensation of an organic polyisocyanate in the presence of acatalytically sufficient amount of methanol and a tertiary aminetrimerization catalyst as hereinafter defined. The products which areproduced in accordance herewith are rigid cellular foam plasticscontaining carbodiimide linkages and isocyanurate linkages. It is thecarbodiimide linkages whose formation provides the carbon dioxideblowing agent and which, together with the isocyanurate linkages,imparts the excellent flame properties to the products.

Tertiary amine trimerization catalysts which areemployed in the presentinvention include l,3,5-tris-(N,N-dialkylaminoalkyl)-s-hexahydrotriazines; the alkylene oxide and wateradducts of l,3,5-tris( N,N- dialkylaminoalkyl)-s-hexahydrotriazines;2,4,6 tris(- dimethylaminomethyl)phenol; por a mixture of oandp-dimethylaminomethylphenol and triethylene diamine or the alkyleneoxide and water adducts thereof. These compounds are well known in theart, as is their use as catalysts which promote isocyanurate linkages.

1,3 ,5-Tris( N ,N-dialkylaminoalkyl )-s-hexahydrotriazine compounds haveheretofore been described as useful -co-catalysts or isocyanatetrimerization catalysts. See US. Pat. No. 3,723,366, the disclosure ofwhich is hereby incorporated by reference. Preferred within this groupof hexahydrotriazine compounds is l,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine.

The alkylene oxide and water adducts of a l,3,5-tris(N,N-dialkylaminoalkyl)-s-hexahydrotriazine is presumably aquaternary ammonium hydroxide. These compounds are generally prepared byreacting equimolar amounts of the hexahydrotriazine, alkylene oxide andwater at a temperature of from about 10 to C. for a period of from about5 minutes to 2 hours. Preferred within this group of compounds is thepropylene oxide and water adduct of l,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine. See US. Pat. Nos. 3,746,709and 3,766,103, the disclosures of which are hereby incorporated byreference.

2,4,6-Tris(dimethylaminomethyl)phenyl as well as o-, pand a mixture ofoand p- (dimethylaminomethyl)-phenol are known compounds which arecommercially available products sold by Rohm & Haas under the tradenames DMP-30 and DMP-lO. Triethylenediamine and the alkylene oxide andwater adducts thereof are also well-known compounds commerciallyavailable under the trade name Dabco.

The amount of trimerization catalyst which may be employed in thepresent invention is generally from 0.1 part to 20 parts of catalyst perI00 parts of organic polyisocyanate. The amount of methanol which isemployed is generally from 0.1 part to 10 parts per parts of organicpolyisocyanate.

The organic polyisocyanate used in the preparation of the foams inaccordance with the present invention corresponds to the formula:

R"(NCO),

wherein R" is a polyvalent organic radical which is either aliphatic,aralkyl, alkaryl, aromatic ormixtures thereof, and z is an integer whichcorresponds to the valence of R" and is at least two. Representative ofthe organic polyisocyanates contemplated herein includes, for example,the aromatic diisocyanates, such as 2,4- toluene diisocyanate,2,6-toluene diisocyanate, mixtures of 2,4- and 2,6-toluene diisocyanate,crude toluene diisocyanate, methylene diphenyl diisocyanate, crudemethylene diphenyl diisocyanate and the like; the aromatictriisocyanates such as 4,4',4"- triphenylmethane triisocyanate,2,4,6-toluene triisocyanates; the aromatic tetraisocyanates, such as4,4- dimethyldiphenylmethane-2,2 '-5 ,5 '-tetraisocyanate, and the like;arylalkyl polyisocyanates, such as xylylene diisocyanate; aliphaticpolyisocyanates, such as hexamethylene-l,S-diisocyanate, lysinediisocyanate methylester and the like; and mixtures thereof. Otherorganic polyisocyanates include polymethylene polyphenylisocyanate,hydrogenated methylene diphenylisocyanate, m-phenylene' diisocyanate,naphthylene-l ,5- diisocyanate, l-methoxyphenyl-2,4-diisocyanate, 4,4-biphenylene diisocyanate, 3 ,3 '-dimethoxy-4 ,4 biphenyl diisocyanate,3,3-dimethyl- 4,4-biphenyl diisocyanate, and3,3'-dimethyldiphenylmethane-4,4'- diisocyanate.

These polyisocyanates are prepared by conventional methods known in theart such as the phosgenation of the corresponding organic amine.

Still another class of organic polyisocyanates contemplated for useherein are the so-called quasiprepolymers. These quasi-prepolymers areprepared by reacting an excess of organic polyisocyanate or mixturesthereof with a minor amount of an active hydrogen containing compound asdetermined by the wellknown Zerewitinoff test, as described by Kohler inJournal Of The American Chemical Society, 49, 3181 (1927). Thesecompounds and their methods of preparation are well known in the art.The use of any one specific active hydrogen compound is not criticalhereto, rather any such compound can be employed herein.

Suitable active hydrogen-containing groups as determined by theZerewitinoff method which are reactive with an isocyanate group includeOH, Nl-l-, COOH, and SH. Examples of suitable types of organic compoundscontaining at least two active hydrogen-containing groups which arereactive with an isocyanate group are hydroxyl terminated polyesters,polyalkylene ether polyols, hydroxyl-terminated polyurethane polymers,polyhydric polythioethers, alkylene oxide adducts ofphosphorus-containing acids, polyacetals, aliphatic polyols, aliphaticthiols including alkane, alkene and alkyne thiols having two or more SHgroups; diamines including both aromatic, aliphatic and heterocyclicdiamines, as well as mixtures thereof. Compounds which contain two ormore different groups within the above-defined classes may also be usedin accordance with the process of the present invention such as, forexample, amino alcohols which contain an amino group and a hydroxylgroup. Also, compounds may be used which contain one SH group and one-OH group as well as those which contain an amino group and a -SH group.

Any suitable hydroxyl-terminated polyester may be used such as areobtained, for example, from polycarboxylic acids and polyhydricalcohols. Any suitable polycarboxylic acid may be used such as oxalicacid, malonic acid, succinic acid, glutaric acid, adipic acid, pimelicacid, suberic acid, azelaic acid, sebacic acid, brassylic acid, thapsicacid, maleic acid, fumaric acid, glutaconic acid, a-hydromuconic acid,,B-hydromuconic acid, a-butyl-a-ethyl-glutaric acid, a,B-diethylsuccinicacid, isophthalic acid, terephthalic acid, hemimellitic acid, and1,4-cyclohexane-dicarboxylic acid. Any suitable polyhydric alcohol,including both aliphatic and aromatic, may be used such as ethyleneglycol, 1,3-propylene glycol, 1,2-propylene glycol, 1,4- butyleneglycol, 1,3-butylene glycol, 1,2-butylene glycol, 1,5-pentanediol,1,4-pentanediol, 1,3-pentanediol, 1,6-hexanediol, 1,7-heptanediol,glycerol, 1,1,1- trimethylolpropane, 1,1,l-trimethylolethane,hexanel,2,6-triol, a-methyl glucoside, pentaerythritol, and sorbitolAlso included within the term polyhydric alcohol are compounds derivedfrom phenol such as 2,- 2,-bis(4-hydroxyphenyl)propane, commonly knownas Bisphenol A.

The hydroxyl-terminated polyester may also be a polyester amide such asis obtained by including some amine or amino alcohol in the reactantsfor the preparation of the polyesters. Thus, polyester amides may beobtained by condensing an amino alcohol such as ethanolamine with thepolycarboxylic acids set forth above, or they may be made using the samecomponents that make up the hydroxyl-terminated polyester with only aportion of the components being a diamine such as ethylenediamine.

Any suitable polyalkylene ether polyol may be used such as thepolymerization product of an alkylene oxide or of an alkylene oxide witha polyhydric alcohol. Any suitable polyhydriic alcohol may be used suchas those disclosed above for use in the preparation of thehydroxylterminated polyesters. Any suitable alkylene oxide may be usedsuch as ethylene oxide, propylene oxide, butylene oxide, amylene oxide,and heteric or block copolymers of these oxides. The polyalkylenepolyether polyols may be prepared from other starting materials such astetrahydrofuran and alkylene oxidetetrahydrofuran copolymers;epihalohydrins such as epichlorohydrin; as well as aralkylene oxidessuch as styrene oxide. The polyalkylene polyether polyols may haveeither primary or secondary hydroxyl groups and, preferably, arepolyethers prepared from alkylene oxides having from 2 to 6 carbon atomssuch as polyethylene ether glycols, polypropylene ether glycols, andpolybutylene ether glycols. The polyalkylene polyether polyols may beprepared by any known process such as, for example, the processdisclosed by Wurtz in 1859 and Encyclopedia Of Chemical Technology, Vol.7, pp. 257262, published by lnterscience Publishers, Inc. (1951) or inU.S. Pat. no. 1,922,459. Alkylene oxide adducts of Mannich condensationproducts are also useful in the invention.

Alkylene oxide adducts of acids of phosphorus which may be used includethose neutral adducts prepared from the alkylene oxides disclosed abovefor use in the preparation of polyalkylene polyether polyols. Acids ofphosphorus which may be used are acids having a P 0 equivalency of fromabout 72 to about The phosphoric acids are preferred.

Any suitable hydroxyl-terminated polyacetal may be used such as, forexample, the reaction product of fromaldehyde or other suitable aldehydewith a dihydric alcohol or an alkylene oxide such as those disclosedabove.

Any suitable aliphatic thiol including alkane thiols containing at leasttwo Sl-l groups may be used such as 1 ,2-ethanedithiol,1,2-propanedithiol, 1,3- propanedithiol, and 1,6-hexanedithiol;alkenethiols such as 2-butene-1,4-dithiol, and alkynethiols such as3-hexyne- 1,6-dithiol.

Any suitable polyamine may be used including aromatic polyamines such asmethylene dianiline, polyarylopolyalkylene polyamine (crude methylenedianiline), p-aminoaniline, 1,5-diaminonaphthalene, and2,4-diaminotolune; aliphatic polyamines such as ethylenediamine,1,3-propylenediamine; l ,4- butylenediamine, and 1,3- butylenediamine,as well as substituted secondary derivatives thereof.

In addition to the above hydroxyl-containing compounds, other compoundswhich may be employed include graft polyols. These polyols are preparedby the in situ polymerization product of a vinyl monomer in a reactivepolyol medium and in the presence of a free radical initiator. Thereaction is generally carried out at a temperature ranging from about40' to 'C.

The reactive polyol medium generally has a molecular weight of at leastabout 500 and a hydroxyl number ranging from about 30 to about 600. Thegraft polyol has a molecular weight of at least about 1500 and aviscosity of less than 40,000 cps. at 10% polymer concentration.

A more comprehensive discussion of the graft polyols and their methodsof preparation can be found in U.S. Pat. Nos. 3,383,351; 3,304,273;3,652,639, and in U.S. patent application Ser. No. 31 1,809 filed Dec.4, 1972,

polyisocyanate and the catalyst at an initiating termperature which,depending on the ctalyst, will range from about to 50 C. Under suchconditions almost immediately an exotherm is developed within thereaction the disclosures of which are hereby incorporated by system,carbon dioxide is generated and foam formareference. tion begins.Alternatively, the foams may be prepared A150 p y Containing ester g pcan be by adding the catalyst to the mixture of polyisocyanate ployed inthe subject invention. These p01yO1S are preand a blowing agent,Optionally, a polyol is blended pared y the reaction of an alkyleneOXide with an with the catalyst and added to the mixture ofpolyisocyganic dicarboxylic acid anhydride and a compound anat and theblowing agent. containing a reactive hydrogen atom. A more compre- Thepresent invention also contemplates the incorhenSiVe discussion of thesep lyol and their meihOd 0f poration of additional ingredients in thefoam formulap p i an be found in 3, 5,1 tion to tailor the propertiesthereof. Thus, plasticizers, 3,639,541 and 3,639,542. As is clear fromthe above, such as tris( 2-chloroethyl) phosphate; surfactants, such theparticular polyol ingredient employed in the prepal as the siliconesurfactants, e.g., alkylpolysiloxanes and ration of the quasiprepolymeris not a critical aspect polyalkyl siloxanes, may be employed in theinvention. of the present invention. Any compound containing at Furtheradditional ingredients include auxiliary or supleast two reactivehydrogen atoms may be so used. plemental blowing agents, such as wateror halohydro- In a preferred embodiment of the present invention,carbons, as described in co-pending U.S. patent applithe condensation ofthe organic polyisocyanate is carcation Ser. No. 169,526, filed Aug. 5,1971. Also, inorried out in the presence of a polyol. Any of the polyolsganic fillers, pigments and the like can be used. discussed above inconnection with the preparation of In any event, the foams prepared inaccordance herethe quasi-prepolymers may be employed in the process withare rigid cellular products having a density of from of the subjectinvention. Generally from 0.01 to 0.5 about 1 pound to 40 pounds percubic foot which exequivalent of a polyol having an averagefunctionality hibit excellent flame properties, such as fire resistance,of 2 to 8 and an average hydroxyl equivalent of from low smoke evolutionand excellent weight retention. about 100 to about 3000 will be employedin the pro- Following are specific, non-limiting examples which cess ofthe subject invention. The use of a polyol results are provided toillustrate the enumerated principles dein foams of reduced friabilitywithout any loss in flame scribed herein. All parts are by weight unlessotherwise retardancy. If a polyol is employed in the invention, aindicated. In the examples, the compressive strength catalytic amount ofa urethane-promoting catalyst may properties of the foams weredetermined in accordance also be employed. These catalysts are wellknown in the with ASTM-1621, the flame retardant properties by art andinclude the metal or organometallic salts of car- ASTMD-30l4 and thefriability properties by ASTM boxylic acid and tertiary amine.Representative of such C-421. compounds are: dibutyltin dilaurate,dibutyltin diacetate, stannous octoate, lead octoate, cobalt naphthen-EXAMPLES ate, and other metal or organometallic salts of carbox- Aseries of foams was prepared by simultaneously ylic acids in which themetal is bismuth, titanium, iron, adding a co-catalyst system to areaction vessel antimony, uranium, cadmium, aluminum, mercury, equippedwith a high speed stirrer to which had been zinc, or nickel as well asother organometallic com- 40 chargedapolyisocyanate and in certaincasesablowing pounds such as are disclosed in U.S. Pat. No. agent. Anexotherm was generated and foam formation 2,846,408. Tertiary aminessuchas triethylenediamine, followed soon after. Table 1, below, illustratesthe detriethylamine, diethylcyclohexylamine, imethyletails of thepreparations. in all cases, infrared spectrothanolamine,methylmorpholine, trimethylpiperazine, scopic analyses indicate that thefoams exhibit carbodi- N-ethylmorpholine and diethylethanolamine mayalso imide and isocyanurate linkages. In Table I the followbe employedas well as mixtures of any of the above. ing abbreviations are employed:Preferred urethane-promoting catalysts are the tin salts of carboxylicacids, such as dibutyltin dilaurate and di- TD] a mixture of 80/20 yweight butyltin dlacetate. Generally, the amount of the ure- 2 4 ,2,6to1y|ene diisocyanate thane-promoting catalyst employed will be from0.01 PAPl po ymethy ene o ypheny jsocya ate part to 10 parts per 100parts of organic polyisocya- TDH nate. DMP-30 2,4,6-tris(dimethylaminomethyl The carbone dioxide-blown foams of the present F4 13ffigf vent1on are prepared by mlxing together the organic ethane TABLE 1Catalyst lsocyanate Blend. Volume Blend, pbw. Cream Rise Exoof Foam phw.Metha- DMP- F-l 13 Time Time therm in Example PAPl TDI nol TDH 30 pbw.sec. sec. C. litres Cream Rise Volume F-l 13 Time Time in pbw. sec. sec.litres Volume Rise Exoof Foam Time them in sec. C. litres erties of someof the resulting foams. in all cases, infrared spectroscopic analysesindicate that the foams exhibit carbodiimide and isocyanurate linkages.In addition to the abbreviations mentioned before, the followingabbreviations are employed in Tables II and III FYROL CEFtris(2-chloroethyl) phosphate DC-l93 polyalkyl siloxane-polyoxyalkylenecopolymer, a foam stabilizer.

TABLE ll Catalyst Blend, pbw.

DMP- FYROL DC- CEF 193 Cream Time nol TDH Methawwwwwwm DMP F-l l 3 30pbw.

TDI

TABLE I Continued Catalyst Blend, pbw. Metha- TDH lsocyanate Blend,

pbw. PAPI ll0llll lll9 l nol lsocyanate Blend, pbw. Example PAPl TDlEXAMPLES 27-43 A series of foams was prepared by simultaneously adding aco-catalyst system to a reaction vessel Example equipped with a highspeed stirrer to which had been charged a polyisocyanate and variousoptional ingredients such as a plasticizer, a surfactant and a blowingagent. An exotherm was generated and foam formation followed soon after.Tables II and III, below, illustrate the details of the preparations aswell as physical prop- 30 TABLE III Physical Properties Of FoamsCompressive Closed Strength Tumbling Cell Butler Chimney Test 10%Friability Content Weight Flame Time Foam of Density Deflection WeightCorrected Retention l leight to SX Example pcf. psi. Loss inches sec.

Amine catalyst employed was triethylcncdiamine 9 10 EXAMPLES 44-54Polyol B a 730 average molecular weight Th f propylene oxide adduct of ePllPWll'lg examples illustrate the preparation of lrimethylolpropanc y ycarbodumlde-lsocyanurate foams prepared in the pres- P l I C $2? of 232)l I ht yo a average mo CU Ell welg ence of certain polyols. The foamswere prepared by polypropylene glycol (hydroxyl mixing at roomtemperature two streams in a metal number of 107) Polyol D a 1560average molecular weight I conta nr and lallowing to foam 1n l0 X 4paper propylene Oxide adduct f boxes. enera y, the mixture foamed inabout two to Irime hylo pr p y y ten seconds and was tack-free m 80-100seconds. One P I I E -2 dd t f M h 0 yo propy one on e a uc 0 annlcstream contained the polylsocyanate and blOWlng agent condensationproduct of one mole while the other stream contained the catalysts,surfac- 10 of Phemb diehamlamine and tant, plasticizer and polyol.Infrared spectroscopic ggfi (hydroxyl number of analyses reveal that thefoams exhibit carbodiimide, Polyol 8495 average molecularweighi ianurate d urethane 1' k propylene oxide adduct ofethyleney l] h m ages.Detalls of the diamine (hydroxyl number of 450) preparations as we as pyslcal properties of the result- 1 5 Polyol G a 2000 average molecularweight mg foams are presented In Table IV, below. In addition glfi ig gi g z l 8 lplC 11C! an utane 10 to the ingredients and amounts thereofset forth in the (hydroxyl ber of 56 TABLE lV Example Ingredients: 44 4546 47 48 49 50 51 52* 53 54** PAP! loo 100 90 100 90 100 90 100 100 100gg l0 l0 10 l0 Pol olB 2 22323: Polyol C 25 Polyol D 7O 20 Polyol E 4Polyol F l; Polyol G 20 h Example phys'cal Pmpemm 44 45 4o 47 48 49 so51 52* 53 54** Density, pcf. 2,0 1.9 L9 1.8 2.2 2.0 2.0 L9 L7 2.3 L9Compressive Strength, 10% 1 22 21 19 2l 17 22 15 28 35 23 TumblingFriability, 71 Welght Loss 2 24 l0 19 21 30 l3 l9 18 21 25 Closed CellContent w Cmmledw 8 9s 9s 9s 96 99 97 98 100 lOO 98 Butler Chimney TestRetention, weight 7 Flame Height. in. g g 9% 90 90 93 93 92 92 1&7 92Time to SX, sec. 10 8 8 6 7 7 7 0 0 l0 l0 l0 10 10 l0 l0 l0 l0Formulation included 0.7 "Formulatinn included 1.0

Table, all foams were prepared employing 2 parts f methanol, l.5 partsof 1,3,5-tris(N,N dimethylaminopropyl)hexahydrotriazine, 18 parts oftrichlorofluoromethane, 1.5 parts of tris(2 chloroethyl) phosphate, 1part of dibutyltin dilaurate and 1 part of silicone surfactant. In TableIV, below, the following new abbreviations are employed:

Polyol A a 775 average molecular weight polypropylene glycol (hydroxylnumber of part of TPH. 0.7 part of DBTDL. 1.2 part of FYROL CEF and 0.7pu 0f M493 part of dlhutyltiniliacctate in lieu of D age functionalityof 2 to 8 and an average hydroxyl equivalent of from about to 3000.

5. The process of claim 4 carried out in the presence of a catalystwhich promotes urethane linkages.

6. The process of claim 5 wherein the catalyst which promotes urethanelinkages is dibutyltin diacetate or dibutyltin dilaurate.

7. The process of claim 1 carried out in the presence of a fluorocarbonblowing agent.

8. The process of claim 1 carried out in the presence of tris(2-chloroethyl) phosphate.

1. A PROCESS FOR THE PREPARATION OF A CELLULAR FOAM CHARACTERIZED BYCARBODIIMIDE AND ISOCYANURATE LINKAGES WHICH COMPRISES CONDENSING ANORGANIC POLYISOCYANATE IN THE PRESENCE OF A CATALYTICALLY SUFFICIENTAMOUNT OF A CATALYST SYSTEM CONSISTING ESSENTIALLY OF METHANOL AND ATERIARY AMINE TRIMERIZATION CATALYST SELECTED FROM THE GROUP CONSISTINGOF 1,3,5TRIS(N,N-DIALKYLAMINOALKYL)-S- HEXAHYDROTRIAZINES, THE ALKYLENEOXIDE AND WATER ADDUCTS THEREOF, AND2,4,6TRIS(DIMETHYLAMINOMETHYL)PHENOL.
 1. A process for the preparationof a cellular foam characterized by carbodiimide and isocyanuratelinkages which comprises condensing an organic polyisocyanate in thepresence of a catalytically sufficient amount of a catalyst systemconsisting essentially of methanol and a tertiary amine trimerizationcatalyst selected from the group consisting of1,3,5-tris(N,N-dialkylaminoalkyl)-s- hexahydrotriazines, the alkyleneoxide and water adducts thereof, and2,4,6-tris(dimethylaminomethyl)phenol.
 2. The process of claim 1 whereinthe organic polyisocyanate is selected from the group consisting oftoluene diisocyanate, methylene diphenyl diisocyanate, polyphenylpolymethylene polyisocyanate and mixtures thereof.
 3. The process ofclaim 1 wherein the tertiary amine is1,3,5-tris(N,N-dimethylaminopropyl)-s-hexahydrotriazine.
 4. The processof claim 1 carried out in the presence of from 0.01 to 0.5 equivalent ofa polyol having a average functionality of 2 to 8 and an averagehydroxyl equivalent of from about 100 to
 3000. 5. The process of claim 4carried out in the presence of a catalyst which promotes urethanelinkages.
 6. The process of claim 5 wherein the catalyst which promotesurethane linkages is dibutyltin diacetate or dibutyltin dilaurate. 7.The process of claim 1 carried out in the presence of a fluorocarbonblowIng agent.